This research grant proposes to test a hypothesis which addresses the problem of basic molecular processes involved in pain. In order to elucidate the molecular process, this research will determine if an antogonistic interaction exists between prostaglandins and enkephalins in tooth pulp tissue. Concentrations of prostaglandins and enkephalins in control pulp tissue will be distinguished versus concentrations in stimulated pulp tissue. Pulpal stimulation will be produced electrically and/or chemically. Enkephalins of interest include leucine-enkephalin, and methionine-enkephalin. The prostaglandin to be studied is a primary pain-related prostaglandin, PGE2. The described methodology can be readily extended to include other peptides and PGs. Biochemical methodology includes extractions of peptides and prostaglandis from tooth pulp tissue, high performance liquid chromatography (HPLC) separation of individual compounds, collection of individual fractions, chemical derivatization of prostaglandins (PGs) for gas chromatography-mass spectrometry (GCMS) studies, and field desorption mass spectrometry (FDMS) of chemically underivatized peptides. Stable isotope-labeled internal standards (IS) will be utilized for quantification of each molecular species. With this scheme, the structure of the peptides and prostaglandin is unambiguously connected with the analytic measurement. This structure-quantity measurement is a signal advancement in analysis of biologic tissue because it removes any ambiguity of measurement. The long-term objectives include description of chemical regulators in nociception. Pain is of great interest in the medical and dental fields and is of great socioeconomic interest.